What is cork taint?

You smell cork taint as damp cardboard, a wet cellar or mould, and in milder cases you mainly notice that the fruit seems to have disappeared from the wine.

The Australian Wine Research Institute describes the smell as distinctly musty and mouldy, and points out that the substance suppresses positive fruit notes even at very low concentrations. A wine that merely tastes dull and short, without you naming anything musty, can therefore also be slightly affected.

Other musty compounds show a comparable picture. For 2,4,6-tribromoanisole the threshold is 4 nanograms per litre, for 2-methoxy-3.5-dimethylpyrazine 2.1 nanograms per litre, for geosmin 25 and for 2-methylisoborneol 30 nanograms per litre. In practice, these all fall under what people call cork.

TCA is one of the strongest-smelling substances in food: a few nanograms per litre suffice, i.e. a few parts per trillion.

The AWRI gives a detection threshold of 1.4 nanograms per litre for pinot noir. For consumers, the threshold at which they notice it is 2.1 nanograms per litre, and the threshold at which they reject the wine is 3.1 nanograms per litre. Some of the institute's tasters notice less than 1 nanogram per litre.

In a 2015 study in the Journal of the Institute of Brewing, twelve trained tasters determined the recognition threshold with a duo-trio test, in series from 0 to 16 nanograms per litre, repeated three times on three different days. After training, they arrived at 3.2 nanograms per litre in water, 4.3 in white wine and 7.6 in red wine.

TCA forms when moulds render chlorophenols harmless by attaching a methyl group to them, after which the substance remains behind in the cork or in wood.

The raw material is usually 2,4,6-trichlorophenol, which gets into the cork via the environment or via chlorine-containing treatments. Moulds of the genera Penicillium, Fusarium and Trichoderma convert that into 2,4,6-trichloroanisole. For the mould that is a defence reaction, for the wine it is a fault.

Cork is not the only source. TCA can also arise in oak barrels without any cork involved, and also via the air in a cellar. A 2022 review holds TCA responsible for 50 to 80 percent or more of all musty faults in wine.

Measurements at large wine competitions come to a few percent, with a clear decline over the last twenty years.

At the International Wine Challenge, all wines that a jury finds suspect are checked by a separate faults clinic. Over the first six years of that clinic, with more than 90,000 wines assessed, 2.7 percent came out of the test as cork taint. In total, 6.4 percent of the wines were judged faulty, of which 1.6 percent brett.

Earlier figures were higher. In an edition of the same assessment in which 12,000 bottles were opened, 4 percent were affected. In a study by the British Wine and Spirit Association, 14,000 bottles were tasted over eighteen months; independent verification confirmed 0.7 to 1.2 percent mustiness and 3.4 percent faults in total.

Sensitivity to TCA varies widely from person to person and wine to wine, and training measurably changes the threshold.

In the 2015 study, the tasters' threshold fell after training from 4.6 to 3.2 nanograms per litre in water and from 6.7 to 4.3 in white wine. In red wine it went the other way, from 7.1 to 7,6, because the wine's own aroma masks the substance. An overview from 2022 even names 22 nanograms per litre as the threshold for red wine.

Even experienced tasters regularly get it wrong. Wine writer Jamie Goode reported that 60 percent of the wines sent to him as faulty turned out, after checking, not to be faulty at all.

Smell first, pour afterwards. If you don’t trust it, close the bottle again and take it back to the shop where you bought it.

Cork taint is a defect of the product and not a matter of personal taste, so a good wine & spirits shop takes such a bottle back. Bring the cork and leave a little wine in the bottle, because an empty bottle can no longer be assessed.

If you doubt whether it is really cork, bring the bottle to us. Here in Bathmen we smell along with you and work out whether it is down to the closure or to something else, such as a closed or sulphurous nose that fades by itself. With a detection threshold of around 1.4 nanograms per litre, this is exactly the kind of judgement where a second nose helps.